JPH05145987

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DESCRIPTION JPH05145987
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is intended to
receive an acoustic wave generated in the water while being supported by the stern of a marine
research vessel or the like at one end and being towed like a wind in the sea. The present
invention relates to a towing piezoelectric cable suitably used for seismic survey and fish school
detection.
[0002]
[Prior Art] A towing piezoelectric cable x used for seafloor seismic survey, fish school detection,
etc. is caught by being connected to a winch u disposed at the stern of a ship s, as shown in FIG.
It is towed freely. The piezoelectric cable x includes a piezoelectric layer made of a sintered
piezoelectric ceramic material, a piezoelectric organic substance or a piezoelectric organic
ceramic, and the piezoelectric layer receives an acoustic wave propagating in water to generate
an output signal. It is.
[0003]
Piezoelectric organic matter such as polyvinylidene fluoride, polyvinylidene fluoride,
polyvinylidene chloride, polyvinyl chloride, nylon etc. or synthetic rubber or ferroelectric resin
such as lead zirconate titanate or lead titanate in organic matter of synthetic resin A piezoelectric
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organic substance or a piezoelectric organic ceramic composite formed by mixing particles has a
characteristic that the acoustic impedance is close to the acoustic impedance of water, and
therefore, when it is used as a piezoelectric layer of the piezoelectric cable x, water is There is an
advantage that the propagating acoustic wave can be efficiently received and the sensitivity can
be enhanced. Therefore, as shown in FIG. 5, a piezoelectric layer h made of the piezoelectric
material is disposed around the electrode core i, and an outer electrode j such as a conductive
paint is disposed on the outer periphery of the piezoelectric layer h. A predetermined DC voltage
is applied between the outer electrodes j to form a coaxial piezoelectric cable x in which the
piezoelectric layer h is polarized in the radial direction, and this is immersed in water, and
between the electrode core i and the outer electrodes j There is one that takes out an output
signal to receive an acoustic wave propagating in the water.
[0004]
By the way, in the conventional piezoelectric cable for towing, the specific gravity of the
piezoelectric layer is about 5.3, and the specific gravity as a whole is larger than that of seawater.
Therefore, since the total length is also about 300 m, a large drop H occurs between the proximal
end and the outer end of the piezoelectric cable when it is towed, as shown in FIG. There is a
problem that it is not possible to obtain an accurate receiving sensitivity because of the influence.
The present invention aims to solve such problems.
[0005]
SUMMARY OF THE INVENTION In the present invention, a metal foam made of metal containing
a glass balloon is used as a core material, and electrodes are formed on the inner and outer
surfaces on the periphery via an insulating layer. It is characterized in that the piezoelectric layer
is formed.
[0006]
Further, in such a basic configuration, this may first be used as a short cable base, and each cable
base may be connected via a flexible node.
[0007]
Furthermore, the core material made of the foam metal may be formed into a polygonal shape in
cross section, and piezoelectric layers having electrodes formed on the inner and outer surfaces
may be disposed on the respective side faces via the insulating layer.
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[0008]
The foam metal has a small specific gravity of about 0.3.
For this reason, by using this as a core material, it becomes possible to lower the specific gravity
of the whole and to make it approximate to the specific gravity of seawater.
Therefore, it is possible to tow almost horizontally, and the difference in water pressure at the
front and rear ends can be reduced as much as possible.
[0009]
By the way, what used the foam metal as a core material does not have flexibility, therefore,
when this is used as it is as a long shape, it can not wind up with a winch.
Therefore, by forming the cable base into a short shape first and connecting each cable base with
the flexible joint, flexibility can be generated as a whole, and winding becomes possible.
[0010]
On the other hand, in the configuration in which the core material made of the metal foam is
formed into a polygonal shape in cross section and the piezoelectric layer is disposed on each
side surface, the piezoelectric layer can be attached later, which facilitates manufacture.
[0011]
1 and 2 show a first embodiment of the present invention.
The towing piezoelectric cable x having such a configuration will be described. Here, 1 is a core
material made of foam metal, which is formed by containing a glass balloon in metal, and the
core wire 2 penetrates the center of the core material 1. Further, an insulating layer 3 made of
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ABS resin is disposed on the outer side of the core member 1, and a piezoelectric layer 4 having
electrodes 5, 6 formed of conductive paint etc. on the inside and the outside is disposed around
the insulating layer 3. Be done.
[0012]
The piezoelectric layer 4 is an organic substance which itself exhibits piezoelectricity, such as
polyvinylidene fluoride, and lead titanate (PbTiO3) in the organic substance of synthetic resin,
and lead zirconate titanate (Pb (Ti · Zr It is formed of a piezoelectric composite obtained by
mixing ferroelectric ceramic particles such as) O3).
[0013]
The piezoelectric cable x formed in this manner has no flexibility because the core material is a
hard foam metal.
Therefore, as shown in FIG. 1, the cable base y is made into a short shape, and each cable base y
is made continuous with the core wire 2 penetrating the center and the core wire 2 exposed
between each short cable body y is a flexible node portion The piezoelectric cable x as a whole is
made flexible by each flexible joint z. Further, the outer electrodes 6 of the respective
piezoelectric layers 4 of the cable substrate y are electrically connected by the conducting wires
7, respectively, and output terminals 8a connected to the core 2 connected to the inner
electrodes 5 and the respective outer electrodes 6 of the same potential. An output signal is
taken out from between 8b.
[0014]
In each of the short cable bases y, a phase difference occurs between the received signals from
the one near the sound wave source and the one from a distant position. Therefore, the direction
of sound can be detected using this phase difference. In this case, different from the abovementioned connection means, it is necessary to separately take out the outputs from the
respective short cable bases y by means of the lead wires, and therefore, it is necessary to have a
configuration which enables taking out a large number of lead wires.
[0015]
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Further, if the core wire 2 is made of a material having characteristics as a superelastic alloy at
normal temperature, the memory shape may be straightened, or the like may be pre-set to an
optimum shape to cause winding by a winch u. Therefore, the shape can be properly maintained,
and the flow noise can be reduced.
[0016]
In such a configuration, the whole is housed in a hose 10 such as vinyl chloride and filled with
the insulating oil 9 such as kerosene, and the hose 10 protects the short cable substrate y from
seawater, thereby piezoelectricity. A cable x is constructed.
Then, in the piezoelectric cable x having such a configuration, as described above, it bends due to
the flexible joint portions z between the short cable bases y and y and has flexibility as a whole,
as shown in FIG. As shown, by being connected to the winch u disposed at the stern of the ship s,
it is towed freely.
[0017]
In the above-described embodiment, as shown in FIG. 1, the piezoelectric cable x is made flexible
so that it can be wound. The piezoelectric cable x can also be configured by the short cable base
y in the above.
[0018]
FIG. 3 shows another configuration.
Here, the core material 11 has a square cross section, and the core wire 12 is inserted through
the center, and the side surfaces of the four circumferences are covered with the insulating layer
13 made of ABS resin, and then the electrodes 15, 16 are provided on the front and back sides.
Are formed by bonding the piezoelectric layers 14, 14. In this configuration, the insulating layer
13 and the piezoelectric layers 14, 14... May be sequentially disposed on the peripheral portions
of the piezoelectric layers 14, 14. In addition, the core material 11 may have a polygonal shape
such as a hexagonal shape, and by increasing the side surfaces in this manner, the connecting
portions of the angular edges of the respective piezoelectric layers 14, 14. It is expected that the
characteristics will be improved and the receiving characteristics will be improved.
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[0019]
In each of the configurations, the core material 1 is made of a foam metal having a small specific
gravity of about 0.3. For this reason, the specific gravity of the entire piezoelectric cable x is also
reduced, and it is possible to approximate it to the specific gravity of seawater, and in the towing
state, the horizontal state can be generated as much as possible in the seawater. The heights of
the proximal end connected to the winch u and the outer end to be wind-slowed can be made
substantially equal, as indicated by the broken line in FIG. Incidentally, since air is contained in
the core member 1, the sensitivity is lowered due to the damping effect due to the frequency
above a certain level, but it has sufficient receiving sensitivity up to 10 KHZ.
[0020]
According to the present invention, since the piezoelectric cable x is constructed by arranging the
piezoelectric layer 4 around the core material 1 made of the foam metal as described above, the
core material 1 can The specific gravity of the whole can be reduced, and by approximating it
with the specific gravity of seawater, the piezoelectric cable x can be made horizontal in the
towing state, and the water level difference between the base end and the tip can be reduced. The
adverse effect of the difference can be eliminated, and an output signal as good as possible can
be obtained. Further, in the case where the short length cable base body y is connected by the
flexible node portion z to constitute the piezoelectric cable x, the winding with the winch u
becomes possible and the handling becomes easy while maintaining the above advantages. is
there. Furthermore, in the configuration in which the core layer 1 has a polygonal shape in cross
section and the piezoelectric layer 4 is disposed on each side surface, the piezoelectric layer 4
can be attached later, which facilitates manufacture. effective.
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